Kinetic energy absorbing device



March 2, 1965 G. E. FREDERICK KINETIC ENERGY ABSORBING DEVICE Griginal Filed June 20, 1960 5 Sheets-Sheet l mm n mw). .Www E MM m r A 4 1 A E ...M .M H E W M m\\ Q\\ w 4%/ r 6 ma kf S w@ E am w \\\\\E\\\\\\ E El A l um @n W`\\ .mmv N@ m@ 1 NQ Wmv %Q\ m,\\ l mm QQ n v\\ ww mm QM. E wml mm 9% NN ms v9 mm QQ wm Qw\` March 2, 1965 G. E. FREDERICK KINETIC ENERGY ABSORBING DEVICE Original Filed June 20, 1960 5 Sheets-Sheet 2 INVENTOR GERGE E. FREDERICK BQQ zum March 2, 1965 G. E. FREDERICK KINETIC ENERGY ABSORBING DEVICE WIMHFH 5 Sheets-Sheet 3 @QW mm aw f @Nvu mm. mm

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March 2, 1965 I G. E. FREDERICK 3,171,546

KINETIC ENERGY BSORBING DEVICE D r- IjQ//z /1/ /////I I 0 l I /34 I I L I III lq: E.. .'Li law/Li /65 G50/26E E. FREDERICK.

March 2, 1965 G. E. FREDERICK 3,171,546

KINETIC ENERGY ABSORBING DEVICE Original Filed June 20, 1960 5 Sheets-Sheet 5 40 TIE E 400%,l 30o 3 T Zbo q Q /00 INVENTOR.

GEORGE E. FREDERICK,

s TRO/ 5 (/NCHES) ,4 Trap/Vey.

United States Patent O 3,171,546 KINETIC ENERGY ABSORBING DEVICE George E. Frederick, South Bend, Ind., assignor to The Bendix Corporation, South Bend, Ind., a corporation of Delaware Original application June 20, 1960, Ser. No. 37,216, now Patent No. 2,994,442, dated Aug. 1, 1961. Divided and this application Apr. 12, 1961, Ser. No. 102,616

2 Claims. (Cl. 213-43) This invention relates to a kinetic energy absorbing device and more particularly, to a draft' gear which is combined with a railway coupling to provide a cushioning effect during draft and buff operations by absorbing a portion of the kinetic energy transmitted between the coupled cars and thereby safeguarding the equipment against damage. The present invention is a division of copending application Serial No. 37,216, led June 20, 1960 now Patent No. 2,944,442, issued August l, 1961.

During coupling operation, when the railway cars are brought together, the one moving and the other stationary, considerable impact forces are brought to bear through the coupling devices on the railway cars, and that portion of this energy which is not absorbed in some suitable manner by cushioning devices, will exert destructive force on the cars in the form of damage to the center sills, the car frame or other portions of the railway car structure. Since the magnitude of these coupling energies is in the order of 400,000 ft. pounds of energy it can be easily appreciated that the forces must be cushioned in some suitable manner to avoid wasteful destruction. Likewise, draft forces i.e. pulling forces between the cars, must be cushioned because of the high momentum involved in order that jarring forces transmitted between the railway cars can be safely absorbed without producing damage to the cars.

One of the objects of the present invention is to provide a draft gear having a cushioning device which will communicate acceptable forces between the cars without producing damage to the center sill. The present invention purposes a cushioning device which absorbs the kinetic energy of the draft and buff in an eflicient manner, and operates in such manner that forces transmitted between the cars are maintained within maximum limits to preclude damage to the cars.

Another object of the invention is to provide a cushioning draft gear which incorporates a frictional means for dissipating a part of the energy, the operation of which is made more efficient during buff and draft gear operations. Another object of the invention is to incorporate a combination friction and pneumatic-hydraulic energy absorbing means wherein a greater proportion of the kinetic energy is dissipated, as distinguished from merely stored, so that following coupling operation the kinetic energy stored is available for restoring the gear but is itself not a source of potential damage.

A further object of the invention is to provide a railway draft gear having a kinetic energy absorbing device which is functionally more efficient in dissipating the kinetic energies of draft and buff operations to minimize damage.

An important feature of the invention lies in its greater efficiency of absorbing energy, and also in determining the maximum load transmitted thereby between the cars if definite proportion of the load transmitted is made available for restoring the device to its ice original condition when the draft and buff forces on the gear are relieved. By virtue of the operation of the hydraulic portion of the unit, it is possible to build up the resistance load to buff or draft forces at a much faster rate so that a greater proportion of the energy is absorbed, but the maximum resistance load from the hydraulic portion of the unit is itself brought within controllable limits so that damage to the draft gear is avoided. A combination of these two considerations, makes for superior draft gear operation which has greater efficiency and embodies internal safety devices which insure freedom from damage to the gear in draft and buff.

Other objects and features of the invention will become more apparent from a consideration of the following description, which proceeds with reference to the accompanying drawings, wherein:

FIGURE 1 illustrates a railway car and two coupled cars is fragmentary View at its opposite ends:

FIGURE 2 is an isometric detail View of the draft gear which incorporates the present invention;

FIGURE 3 is a top view of the draft gear, showing the coupling member at one end thereof, the center sill of the car being broken away and a portion of the structure being show in section to illustrated the yoke, follower plate, and location of the draft gear between its stops;

FIGURE 4 is a section View taken on line 4-4 of FIGURE 3;

FIGURE 5 is an enlarged detail sectional view throughout the length of the gear and illustrating the cushioning device which is embodied within the draft gear. The gear incorporates one suitable friction means which forms a part of the kinetic energy absorbing media;

FIGURE 6 is an end View of FIGURE 5 looking in the direction oft he arrows 6-6 in FIGURE 5;

FIGURE 7 is an enlarged detail view showing in section a second embodiment of the invention illustrating a different friction means which can be used with the air-hydraulic unit shown in FIGURE 5;

FIGURE 8 is a top view of the embodiment shown in FIGURE 7, the upper half of the view being shown in section taken midway through the device;

FIGURE 9 is a view similar to FIGURE 7 but, show-v ing the relationship of the components during compression stroke as it appears during draft or buflng operation.

FIGURE l0 is an end view of FIGURE 7 looking in the direction of the arrows 10-10 in FIGURE 7;

FIGURE 1l is a further embodiment of the invention showing a different frictional means which can be used with an air-hydraulic unit shown in FIGURE 5;

FIGURE l2 is an end view of the embodiment shown in FIGURE 11, looking in the direction of the arrows 12-12 in FIGURE 1l; and

FIGURE 13 is a Load vs. Stroke graph which shows the energy absorbing characteristics of the present invention and compares it with the curve obtained with a conventionally used prior art device. From these curves efficiency as well as operating characteristics can be interpreted.

Referring now to the drawings, there is shown in FIGURE 1 a box car 10 which is coupled with cars 12 and -14 at its ends 16 and 18 through draft gears 20 and 22. The draft gears 20 and 22 are coupled with cars 12 and 14 through similar gears 24 and 26.

Referring next to FIGURE 2, an isometric View of the draft gear, and its connecting Structure, and to FIGURES which limits contraction of the draft gear in the event of failure of the cusioning device which is designated generally by reference numeral 30. The draft bar 29 having a coupling element 32 is passed' through an opening 34 (FIGURES 3 and 4) and bears at its end 36 against a .follower plate 38 which in turn bearsV against a stop 40 provided `by thefcenter sill 26 thereby preventing movementof the follower plate 38 leftwardly from the position shown in FIGURES 2,3 and 4.

The draft bar 29 has a flat key 42 'which is passed through an opening 441of the draftbar'29 and is fastened thereto, the fiat key 42 being passed through an elongated opening 44 in yoke 46. The yoke 46 is drawn leftwardly (FIGURES, 2, 3 and 4)y by leftward movement of the draft bar 29, but remains stationary when thedraft bar 29 moves rightwardly since the iiatkey 42 thenv moves within elongated opening 44. The end 48 of theyoke 46 is in abutting relation with the base 50 of casing 52 which forms apart of the cushioning devicev 30 and the base 50 bears against flanges 53 whichform a party of the center sill structure 26 and are rigidly secured thereto. Thus, during bu operation which is represented by the solidline` arrow in FIGURES 2,3 and 4 the draft bar 29 communicates load through its end 60 to follower plate 38v which-in turn acts against the end 62 of thecushioning device 30 which is held against movementby engagement of base 50 with stops 53. Since the buff vforces are communicated tor` the car through the cushioning device30 then a major partof the kineticfenergy which 4 sembled, the wedge 76 is biassed inwardly against resistance of the internal 'structure (which will later be described) of the cushioning device 30 and the tendency of that stored energy to extend the device is limited by engagement of the lugs 36 withlugs-84.

As shown'iny FIGURE 5,v the shoes 74 engage the plugged'end 90 of a tubular member 92 having a diaphragm 94 with metering orifice 96 therein. Between the tubular member 92 and casing 52 is a bearing 98 Vhaving seal 10.0.. Within the tubular member 92 is a floating piston 102 `having a seal 104, the piston 102 being amovable wall which separates the interior of the tubular member two variable volume chambersl Ione is involved in the process of car coupling, will be dissipated without producing destructive forces on thevrailway car; thus, shouldthe car 10 be stationary Yandthe car 14 moving rightwardly (FIGURE 1,) as the trainmoves into coupling Vrelation with the stationary car 10 `and its connected car 12, the cars 10Y and` 14 will becoupled and the buff forces dissipated through the device 30. During vdraft operation,A assuming thatA the. train .Yis'mroving leftwardly inVFIGURE 1, should-the car l10.1ag behind the drawing car- 14 with which it is coupled,l there will be produced. a pulling forcev in the direction of .the dotted line' arrows yin FIGURES 2, Sand 4 in whichcase, the ydraft bar 29 moves-y the flat key .'42 leftwardlyin FIG- URES 3 and 4 pulling the yoke 46 therewith. The end 48 of the yoke 46.ac ts against base 50 ofthe cushioning device 30 and the cushioning device 30 anchors throughv n its end 62on-follower plate 38 which is held by abutment 40 secured lto ythe center sill 226. InLthis'manner-,jthe draft forces are communicated through cushioning device 30,

before they are transmitted to the car 10- through abutment 40 in center sill 26 and thus cushioning prevents destructiveforces acting onthedrawn end ofthe car.V

,Referring next toy FIGURES `5 and, 6', there are shown details of the `construction of cushioning. device 30 which isv a combinationk of ,frictionaL pneumatici-'and hydraulic energy absorption media. The device 30 includes Ya easing 52 having lthreesp'aced 'internal friction surfaces `72k (FIGURE 6), which are located about 120 apart one, from the other. .The three friction surfaces 72 have'friction shoes 74 which` are contoured to fitV flatly a hydraulic chamber 105 `and the otherV a pneumatic chamber 1061which is charged with air through an air A second variable volume chamber 110 delined by the interior of the casing 52 is also filled with hydraulic fluid and is communicated with' chamber 105, through the,V metering orifice 96.y yMetering `pin 11,2 having .a longitudinal passage 113 and radial passagellS opening into chambers. 105 and 1,10V4 respectively (FIGURE 5) is `mounted in end wall 114 through threaded connection V116 and is movable through the metering oriice96 to `controlthe effective metering area and determine resistance to hydraulic flow fromv chamber .110 to chamber 105 through Vthe orifice 96. Y

Between the tubular member 92 and the inner surface of casing 52 is an annular chamber 118 which communi- ,cafes with. thev chamber 1,05.throughopenings120. The chamber V118 is an expandingV chamber during' contractionofithei cushioning device y30 andV fluid is exhausted from chamber 118 as the cushioning device l30 elongates.

' A snubbing device 122 is movable against stop 123 during expansion of KVthe chamber by contractile move- Vment of. thedevice 30 toallow freedom of uid flow within the .chamber V1,18 and: the snubbingdevice l122 is caused' toseat against anannular ring nut 125 tov close the -openings 120` during elongationof the. cushioning the rateja'of extensionof thepcushioning device 30 and thereby prevent damage.

vThere is further provided within thev end wall 114 a spring loaded relief valve 1,29 .which vents Huid directly from chamber 110 toj chamber'105 through passages 115 and113in v,the event Vthat excessive .coupling forcesdei'rfelop excessive fluid pressures i'n y,chamber 110. The 50 operation [of theV 'coupling device willrbe next considered.

.Operation of the device i During either buff or draft operations,fforce is communicated frornjthe coupling member 32 to the car through the cushioning device 30.Y In vbringing the railwayV car to a different velocity ie., ,changing its momentum, force.islinevitablybrought to bearon the cars, but, as it will-be 'seen/,j the 'cushioning device,` determines the rate against their opposed friction surfaces 72 andare slidable along the lengthof surfaces 72 by a wedge76halving mundedfprkojetios 7s (FIG-URE 6) extending within eachsho'e. The companion surfaces 80v and 82fof-the shoes and wedge respectively, are tapered, as vshown in FIGU-RE 5 so that. the wedge 76'developsf'abiasing effect, thrusting the shoes 74 outwardly against the fopposed Vfriction `surfaces 72 of they casing 52.v

Lugs 84 are formed' integrally with the end of the casing 52 and'l project radially'inwardly to'provide limit stops lwhich are engaged by lugs 86 on the vwedge 76' therebydeningthe limit of extension ofthe cushioning n device 3.0. That. is, at the time that thedevice 30 is as- .change inrrnomenturn which `is communicated to the car, 4and absorbs at least a portion of the impact during they periodthatV the car isy changing ,its Vmomentum to. prevent damage. When impacts are developed on couv pling member 32 either in buff (toward thev right in FIG- URE 3') or draft (toward the7left in FIGURE 3) force istcommunicated,-tojtherailyvaypcar through the cushiondevieeffv50-rto produce-a telescoping movementy ofthe cushioning device 30., Assuming buff loads, the base 50 f ifs-held stationaryragainst stops53y and the :wedge y76 isfr'ced Vtoward the Vright bythe draft bar 6'0 and'followenplate 3,8.r Referring to FIGURE 13l which visi a Load vsl, Stroke curve, they resistance` to fluid metering from chamber 110.to chamber 1051 will immediately bel-,effec- 1 tivevto opposelongitudinal movement of the shoes 74 towardvtherightfby virtue oftheir engagement withrend of thel tubular member V92;.a`rid` thisy co'unterreaction '5 to the force' developed on wedge 76 will effect radially outward thrust on the shoes 74 against their opposed friction surfaces 72 of the casing. Slidable movement of the shoes 74 on surfaces 72 will develop frictional heat which dissipates a part of the kinetic energy communicated to the car.

In operation, approximately twenty-five to forty percent of the kinetic energy absorbed by the cushioning device 30 is absorbed frictionally in the manner described. The efficiency of operation of the shoes 74 is determined, at least in part, by developing a high normal load between the shoes and their opposing frictional surface from the very beginning of the stroke of the cushioning device; and also sustaining such normal load over the entire stroke length of the cushioning device. Because the hydraulic device develops an almost immediate counterreaction to telescoping movement and such counterreaction is communicated immediately to the shoes through the tubular member 92 as a force opposing their movement, the input force on the end 62 of the wedge 76 will develop at the very beginning of the stroke a substantial degree of spreading movement of the shoes which is a function of the metering resistance through orifice 96.

In FIGURE 13 the area under the curve represents the amount of Work absorbed by the device 30 and the area under the curve divided by the area under a horizontal line passing through the maximum resistance force is a measure of the efciency of the device. The area between the full line and dotted line hump curves represents the energy absorbed frictionally and it will be seen from the curve that the frictional work increases rapidly from the start of the stroke to a maximum, continues unabated and then falls off rapidly only at the end of the stroke. This rapid rise of frictional resistance accounts for the greater efficiency in dissipa-ting the impact loads by means of the frictional media. Heretofore, variable resistance members were provided as the backing for the friction shoes 74 and since the counteraction force on shoes 74 is variable, building up to a maximum as shown by the curve labelled B FIGURE 13, `the normal load of engagement of the shoes builds up gradually and hence during operation of the cushioning device frictional absorption of energy is ineffectual until the terminal part of the stroke. Inevitably, the device is made more inefficient. In the present invention, however, by means of the novel cooperation between the hydraulic and pneumatic cushioning device Which backs up the friction shoes 74 there is a substantially constant resistance force to slidable movement of the shoes 74 which develops a substantially constant normal force of engagement between the shoes 74 and their opposing surface and therefore more efficient usage can be made of frictional dissipation of the kinetic energy.

That portion of the energy which is not dissipated frictionally, is communicated from shoes 74 to the tubular member 92 causing its telescoping movement toward the right in FIGURE thereby exhausting fiuid from chamber 110 through orifice 96 into chamber 10S which is an expanding chamber. Both of the chambers 105 and 110 are completely filled with fluid and although their relative volumes will change during operation, the loss of volume of one is balanced by an enlargement in volume of the other. The resi-stance to stroking or telescoping movement of the cushioning device through the metering orifice 96 is shown in FIGURE 13 and the load value is determined by suitable contouring of the metering pin 112. It is characteristic of metering pin devices, that the load will rapidly increase to a predetermined value which will occur at the beginning of the stroke and will continue substantially undiminished until the end of the stroke. It is thus possible, to determine the maximum force which is communicated through the cushioning device to the center sill of the car by contouring the metering pin 112 in orifice 96 the upper limit of the pressure being fixed by operation of the check Valve 129; Thus, in FIGURE 13, the upper limit of load taken through the cushioning device will not exceed about 500,000 lbs. and any force in excess of this is taken by bottoming out of the follower plate 38 on the casing 52 which transmits the load directly to the center sill through stops 53. These figures are in no Way limitative of the invention, but merely illustrate how the invention can be used to advantage from knowing what the maximum fluid pressure value is and then constructing the metering pin, orifice and check valve so as not to exceed that value.

The energy which is absorbed by meter-ing of fluid from chamber 110 to chamber 105 through orifice 96 and the energy absorbed by compressing the pneumatic charge is represented by the area under the dotted curve labelled A in FIGURE 13; the area between the full line curve A and dotted line A is the energy absorbed frictionally, and the efiiciency of the device is measured by the percentage that the total area under the curve bears to the entire area bounded by a horizontal line taken through the maximum load value. Since a spring force load is zero at the beginning of the stroke and increases at a substantially constant slope to a maximum value, there is produced a different shape curve represented typically by the curve labelled B in FIGURE 13.

Comparing the respective areas bounded by curves A and B it will be seen that area B is considerably smaller than the area A which generally approaches 75-85% efficiency during operation. The curve B was obtained with a Miner draft gear class RF75M and was designed for a 36 pocket and included a rubber plate media spring return. The total energy absorbed was 75,375 ft.lbs. vs. a total of 110,833 ft.l\bs. of energy absorbed by the same size draft gear constructed in accordance with the present invention. Testing Was performed with a 27,000 lb. hammer and the stroke length for each device was approximately 41/2 inches. The energy frictionally absorbed by the draft gear under curve B Was 59,169 ft.libs. and the recoil energy Wlas 16,206 ft.l|bs. representing 21.5% of the total energy. From a comparison of the two draft gears, in FIGURE 13, it is apparent that through a given stroke, a greater amount of kinetic energy can be absorbed by means of a hydraulic device than by a spring device and the energy absorbed by the hydraulic portion of the device, is completely dissipated and is not merely stored as is the case with a spring force so that the problem of releasing such stored energy is not present. Importantly, the resistance to stroking of the device builds up to a near maximum at the very beginning of the operation so that high normal loads are obtained for the friction shoes thus leading to greater efficiency in utilization of the frictional media. During stroking of the tubular member 92 the fluid entering chamber biasses piston 102 (FIGURE 5 toward the left thereby compresisng the air in chamber 106 which has previously charged to about 630 p.s.i. That portion of the kinetic energy which is not frictionally dissipated, nor hydraulically dissipa-ted by the metering action, is stored in the form of compression of the air Within chamber 106 by the floating piston 102.

When the coupling forces are relieved, the cushioning device is extended by means of the compressed charge of air within chamber 106 which develops return forces in the order of eight Ito ten thousand pounds force. The piston 102 is forced toward the right, exhausting fluid from chamber 105 and returning it to chamber 110 through the orifice 96, the chamber 110 being expanded by the admitted flu-id. The fluid entering chamber 110 from chamber 10S reacts against the orifice diaphragm 94 thus causing extension of the cushioning device until follower plate 38 is brought into engagement with its stop 40 (FIGURE 3) and the base 50 is in engagement with its stop S2. A typical stroke length for the cushioning device is about 4-5 inches of travel and if the travel should be in excess of this then the follower plate 38 having inclinedV surfaces 162Y engages the end of the casing 52 and force is communicated directly to the centervsill 26 through stops 52. In

bothbif and draft operations, the follower plate will engage the casing when the stroke is in excess of a predete'rir'iined amount or exceeds a predetermined force whereupon force is transmitted directly to thefcenter sill and bypasses the cushioning effect.

Referring next to the embodiment in FIGURESl 7 through 10, it will be seen that different frictional dissipating means can be combined with an air-hydraulic energy absorption device of the typeshown in FIGURE 5. The frictional portion of the gear is adopted from one constructed by Cardwell Westinghouse and identified as Westinghouse Type NZ-l l-F friction draft gear.

An inner wedge member 130 having tapered sur-faces 132 engages Wedges 41-34 and the wedges have inclinedv faces 136 to force friction members 138 outwardly so that the4 shoes 140 are clamped between friction members i1258 and friction members 1'42vwhich are retained by casing 144. The end 146 of inner wedge memberV 130` is displaced from the ends 148 of the shoes by the distance D so that the inner wedge 130 and wedge 134Y are moved through the distance D before contact ismade withy the ends 1 48 of the shoes 140. The inner wedge 130 has an'end 150 which engages stem 152 and displaces it against the resistance of spring 154. Relative movement ofV the inner wedge 130 through the distance D effects outward camming movement offrictionrnembers 138 through the wedge 134 therebyI clamping the shoes 140 between friction Vmembers 138 and 142. After the inner wedge 130 travels through the distance D contact is then made with the shoes 140 which are backed up by the tubular member 92 the same as in the previousY embodiment and the constancy of the backup force which is developed from they hydraulic portion ,of the unit produces a constancy of .frictional energy dissipation. The

coupling forces move the components of the device from their relative positions shown in FIGURE 7 to the positions shown in FIGURE 9. When theV coupling forces are relieved, the spring 154 (FIGURE 9) biasses the inner wedge member 130 retractively (leftwardly) and thereby assists in frictionally disengaging the outer wedge 134 from the friction member 138 thereby lreleasing clamping of shoes 140 between the friction membersj138 and 142 'and thereby permitting the compressed air within chamber 106 to extend the device. The releasing spring 154 and its related means stem 152, lend 150 and inner lwedge V130 insure an adequate disengagement of thel friction members from theshoes so that the shoes will not be wedged-in place between the friction members to resist release with a force greater than the return force or restoring force from the compressed air in chamber 10'6.

Y Therembodiment shownin FIGURES 7-10 operates similarly to the embodiment Ypreviously described with the exception that vthe frictional means for dissipating a portion of the kinetic energy isprovided by means yof two shoes 140; but, the cooperation between the hydraulic and pneumatic portion of the Vunit and the friction means remains the 'same in that a greater efficiencyof frictional dissipation o-f the coupling energy is realized as well as. the improved hydraulic-pneumatic operation-per-fseV Referring next Vto the embodiment 4shown ingFIGURES 11 and 12, a further variation of frictional means is' shown which is suitable ,for use in connection withthe air-hydraulic portion of the de vice in FIGURE 5. The frictional means is taken from a Waugh-,Gould Type 420 friction draft gear manufactured by Waugh Equipment Company. vThe frictional` absorbing mean in FIGURES 11 and 12 comprises two frictional .shoes-"160 and 161v and 164 which are in sliding engagement with surfaces 166 and 168 of casingr170. Leaf springs 172 and 174 are formed in stacks to effect a spreadingaction on the shoes 160 and 161 to produce trictional engagement between the shoes 160, 1615and their opposed surfaces 166 and 168 provided by casing 174).l

8r The main source of normal load between the shoes V160, 161andl the opposed casing is derived from counter reaction from the end 90 of tubular member 92,. so that as the end 176`of the draft -bar is moved toward the right, the counte'rreaction from the pneumatic-hydraulic ymeans increases the normal load and any longitudinal movementof the end 176 toward the 'right Willdevelop a frictionalresistancelwliich dissipates a part of the buff or draft momentum. TheV balance of the momentum is absorbed by the pneumatic-hydraulic portion of the unit which may be the same" as that provided in the previously described embodiment. This will illustrate, Vthat a substantial variety of frictional' means can be used in con- 'junctionv with a pneumatic-hydraulic Vunit and the benefits of the invention will be retained because of the high value of counterreaction vforce from the hydraulic unit which will produce an almost immediate high order of frictional resistance which will be sustained at a high level throughout the major portion of the buff or draft operation and hence the same degree of improvement in the frictional operation of the gears obtained as described by vir'tue of the high order of normal load vbetween the frictionsurfaces which is sustained substantially constant during draft gear operation in order to obtain maximum utility from the friction members.

Although the invention has been described, in conjunction with but 'a ,few selected embodiments of the invention', it will become apparent to those skilled in the art, that numerous modifications and revisions can -be made while yety incorporating the principles herein disclosed. It is intended therefore, that such variations and revisions of Vthe invention ascan be expected on the part of those skilled in the art, and which incorporate the herein disclosed principles, will be included within the' scope of the following claims as equivalents of the invention.`

What is claimed is:

-iber for bypassing Huid tofsaid other chamber after a predetermined pressure is reached in said one chamber, said relief Yvalve means having a rst iiui'd connection with said one chamber at a right angle to the longitudinal axis of said'one chamber such that 'said fluid pressure responsive relief valve means as adaptedvto open for `bypassing fsaid fiui'd when a predetermined substantially turbulent free pressure is sensed in said first fluid connection, and

a'second fluid connection from said relief valve means to said other chamber to define passage between said chambers that" is operativelyl controlled by said pressure responsive means to bypass Yfluid between said-one chamber and said other chamber independently of said orifice.

2.7,A hydraulic cushioning device comprising two tele- 'scoping members deningtwo Varaible volume chambers, one of'saidy variableY volume chambers being reducible V`in volume toex-haust fluid therefrom during inward telescoping movementfof rone of said lmembers with-.respect 'to the other, 'means providing a metering orifice connect- Y ingv said chambers and throughk which fiuidis -rnetered as it is being exhausted from one chamber to the other Vof said chambers, YaY metering pink forrvariably controlling the area ofsaidmetering orifice during'the telescoping movement ofzone-of said members withY respect to the other, said'rneteringv pin having'an axial-,passage terminating Ain a cavity'atthefbase thereof where vit is Vjoined to Vvone of saidtelescoping members, a springbiased fiuid pressure responsive vrelief valvemea'ns disposed in Ysaid cavity ef said metering pin for controlling the axial passage of said metering pin in the bypassing of fluid from said one chamber to said other chamber after a predetermined pressure is reached in said one chamber, said relief valve means being controlled by a predetermined substantially turbulent free pressure which is directed thereto by a uid connection with said one chamber that is disposed at a right angle to the longitudinal axis of said one chamber `and said metering pin such that when said predetermined substantially turbulent free pressure is sensed in said first uid connection said pressure responsive relief valve means will open to communicate uid in said one chamber with the passage within said meter- 10 ing pin between said chambers to bypass fluid between said one chamber and said other chamber independently of said orifice.

References Cited in the le of this patent UNITED STATES PATENTS 2,363,867 Isely Nov. 28, 1944 2,737,301 Thornhill Mar. 6, 1956 2,928,670 Schnitzer Mar. 15, 1960 2,947,386 Schnitzer Aug. 2, 1960 2,963,175 Thornhill Dec. 6, 1960 2,994,442 Frederick Aug. 1, 1961 

1. A HYDRAULIC CUSHIONING DEVICE COMPRISING TWO TELESCOPING MEMBERS DEFINING TWO VARIABLE VOLUME CHAMBERS, ONE OF SAID VARIABLE VOLUME CHAMBERS BEING REDUCIBLE IN VOLUME TO EXHAUST FLUID THEREFROM DURING INWARD TELESCOPING MOVEMENT OF ONE OF SAID MEMBERS WITH RESPECT TO THE OTHER, MEANS PROVIDING A METERING ORIFICE CONNECTING SAID CHAMBERS AND THROUGH WHICH FLUID IS METERED AS IT IS BEING EXHAUSTED FROM ONE CHAMBER TO THE OTHER OF SAID CHAMBERS, A SPRING BIASED FLUID PRESSURE RESPONSIVE RELIEF VALVE MEANS DISPOSED IN SAID ONE CHAMBER FOR BYPASSING FLUID TO SAID OTHER CHAMBER AFTER A PREDETERMINED PRESSURE IS REACHED IN SAID ONE CHAMBER, SAID RELIEF VALVE MEANS HAVING A FIRST FLUID CONNECTION WITH SAID ONE CHAMBER AT A RIGHT ANGLE TO THE LONGITUDINAL AXIS OF SAID ONE CHAMBER SUCH THAT SAID FLUID PRESSURE RESPON- 